Driving device made of shape-memory alloy

ABSTRACT

A storing section ( 70 ) stores a second initial contact instruction value, which is predefined as an instruction value for positioning a movable portion ( 5 ) to a second contact position where the movable portion ( 5 ) is contacted with a stopper ( 8 ), and an initial standby instruction value, which is predefined as an instruction value for positioning the movable portion ( 5 ) to a specified standby position within a moving range of the movable portion ( 5 ). A correcting section ( 42 ) calculates an actual standby instruction value by correcting the initial standby instruction value, based on a second actual contact instruction value obtained when a contact detection section ( 41 ) has detected that the movable portion ( 5 ) is positioned to the second contact position, and the second initial contact instruction value. A setting section ( 43 ) sets a standby position corresponding to the actual standby instruction value, as an actual standby position of the movable portion ( 5 ).

RELATED APPLICATIONS

This is a U.S. National Phase under 35 U.S.C. §371 of InternationalApplication No. PCT/JP2009/050388, filed Jan. 14, 2009, which claimspriority to Japanese Patent Application No. 2008-005840, filed Jan. 15,2008.

TECHNICAL FIELD

The present invention relates to a shape memory alloy driving device formoving a movable portion by utilizing the shape restoring ability of ashape memory alloy.

BACKGROUND ART

In recent years, an image pickup device employs a technology, wherein amovable portion for holding an image pickup lens is moved by utilizingthe shape restoring ability of a shape memory alloy to position theimage pickup lens. A shape memory alloy, however, has a drawback that itis impossible to start moving a movable portion immediately after startof energization of a shape memory alloy member, because the shape memoryalloy member is not deformed unless heated over a predeterminedtemperature. Patent literature 1 discloses an improved technology,wherein the response speed of a movable portion is increased byenergizing a shape memory alloy member in a standby state before startof driving the movable portion to a targeted position.

However, in the case where a movable portion is positioned by utilizingthe shape restoring ability of a shape memory alloy, positionaldisplacement may occur resulting from e.g. a change in thecharacteristic of the shape memory alloy due to a change in the ambienttemperature or deterioration of the shape memory alloy, or deteriorationof a moving mechanism portion for moving the movable portion.Accordingly, it has been difficult or impossible to apply a shape memoryalloy to a device that requires positional precision, particularly animage pickup device designed such that an image pickup lens is requiredto be positioned to a standby position with high precision.

Patent literature 1: JP 2001-263221A

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a shape memory alloydriving device capable of precisely positioning a movable portion to aspecified standby position.

A shape memory alloy driving device includes: a movable portion; amoving mechanism portion which includes a shape memory alloy member, andmoves the movable portion; a restraining member which is contactablewith the movable portion to thereby restrain a movement of the movableportion, and defines a moving range of the movable portion; a drivecontrol section which outputs a drive signal in accordance with aninstruction value for positioning the movable portion to the shapememory alloy member, and controls the moving mechanism portion to movethe movable portion by deforming the shape of the shape memory alloymember; a contact detecting section which detects whether the movableportion is positioned to a contact portion in contact with therestraining member; a storing section which stores initial positioninformation for determining a relation between a position of the movableportion and an instruction value in an initial state; a correctingsection which calculates an actual standby instruction value, based onan actual contact instruction value obtained when the contact detectingsection has detected that the movable portion is positioned to thecontact portion, and the initial position information; and a settingsection which sets a standby position corresponding to the actualstandby instruction value, as an actual standby position of the movableportion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external construction diagram of a shape memory alloydriving device embodying the invention.

FIG. 2 is a block diagram of a control circuit.

FIG. 3 is a graph showing a relation between a position of a movableportion, and a resistance value of a shape memory alloy member.

FIG. 4 is a graph showing a relation between a position of the movableportion, and a drive current to be applied to the shape memory alloymember.

FIG. 5 is a graph showing a relation between an instruction value to beoutputted from a microcomputer section, and a resistance value of theshape memory alloy member.

FIG. 6 is a graph showing a relation between an instruction value to beoutputted from the microcomputer section, and a drive current to beapplied to the shape memory alloy member.

FIG. 7 is a graph showing a relation between an instruction value to beoutputted from the microcomputer section, and a position of the movableportion.

FIG. 8 is a diagram showing a relation between a position of the movableportion, and an instruction value.

FIG. 9 is a flowchart showing an initial sequence.

FIG. 10 is a flowchart showing a correction process.

FIG. 11 is an external construction diagram of a shape memory alloydriving device provided with contact sensors.

FIG. 12 is a block diagram of a control circuit shown in FIG. 11.

FIG. 13 is a diagram showing a relation between a position of a movableportion, and an instruction value.

FIG. 14 is a flowchart showing an initial sequence.

FIG. 15 is a flowchart showing a correction process.

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment)

In the following, a shape memory alloy driving device as the firstembodiment of the invention is described referring to the drawings. Inthe following description, described is an example, wherein the shapememory alloy driving device is applied to an image pickup device. FIG. 1is an external construction diagram of the shape memory alloy drivingdevice. The shape memory alloy driving device includes a shape memorymember 1, fixing portions 2, a bias spring 3, a lens 4, a movableportion 5, a guide shaft 6, stoppers 7 and 8, conductive wires 9, and acontrol circuit 10. The shape memory alloy member 1, the bias spring 3,and the guide shaft 6 correspond to an example of a moving mechanismportion, and the stoppers 7 and 8 correspond to an example ofrestraining members.

The shape memory alloy member 1 is a wire member extending in thevertical direction, and has an upper end thereof connected to a rightend of the movable portion 5, and a lower end thereof connected to thelower fixing portion 2. The shape memory alloy member 1 is contracted tobe restored into a specified memorized shape when heated over apredetermined temperature, and moves the movable portion 5 in thedownward direction by a contracting force thereof. Further, both ends ofthe shape memory alloy member 1 are connected to the control circuit 10through the conductive wires 9. The shape memory alloy member 1 isenergized and heated by application of a drive current from the controlcircuit 10.

The fixing portions 2 are a pair of upper and lower fixing portions 2and 2 which are fixedly attached to a casing of the image pickup device.The upper fixing portion 2 is connected to the stopper 7 and the biasspring 3, and the lower fixing portion 2 is connected to the stopper 8and the shape memory alloy member 1. Further, the upper fixing portion 2is formed with a hole (not shown) for guiding light from a subject tothe lens 4, and the lower fixing portion 2 is formed with a hole (notshown) for guiding a subject light image formed by the lens 4 to animage sensor 80 (see FIG. 2).

The bias spring 3 has an upper end thereof connected to the upper fixingportion 2, and a lower end thereof connected to the right end of themovable portion 5 to apply an upward stress to the shape memory alloymember 1 so that the contracted shape memory alloy member 1 is extendedin the upward direction to thereby move the movable portion 5 in theupward direction. The lens 4 is constituted of e.g. a convex lens. Thelens 4 focuses light from a subject and guides the subject light imageto the image sensor 80.

The movable portion 5 includes a movable main body 51 and a holdingportion 52. The movable portion 5 is moved in the downward directionalong the guide shaft 6 by a contracting force of the shape memory alloymember 1, and is moved in the upward direction along the guide shaft 6by a bias force of the bias spring 3, whereby the lens 4 is moved in theupward and downward directions.

The movable main body 51 is formed with a through-hole extending in thevertical direction, and the guide shaft 6 is passed through thethrough-hole. The holding portion 52 extends from a generally verticallycenter position on a right surface of the movable main body 51 in therightward direction, and holds the circular lens 4 in such a manner asto enclose the perimeter of the lens 4. An upper portion of a right endof the holding portion 52 is connected to a lower end of the bias spring3, and a lower portion of the right end of the holding portion 52 isconnected to the shape memory alloy member 1.

The guide shaft 6 is a rod-like member extending in the verticaldirection, and has an upper end thereof connected to a lower surface ofthe stopper 7, and a lower end thereof connected to an upper surface ofthe stopper 8. The movable portion 5 is moved in the upward and downwarddirections while being guided along the guide shaft 6.

The stopper 7 has e.g. a rectangular parallelepiped shape or acylindrical shape, and has an upper surface thereof fixedly attached tothe upper fixing portion 2. The stopper 7 is contactable with an uppersurface of the movable main body 51 to thereby restrict an upwardmovement of the movable portion 5. Thus, the stopper 7 defines the upperlimit of the moving range of the movable portion 5.

The stopper 8 has e.g. a rectangular parallelepiped shape or acylindrical shape, and has a lower surface thereof fixedly attached tothe lower fixing portion 2. The stopper 8 is contactable with a lowersurface of the movable main body 51 to thereby restrict a downwardmovement of the movable portion 5. Thus, the stopper 8 defines the lowerlimit of the moving range of the movable portion 5.

In the above arrangement, when the shape memory alloy member 1 iscontracted/hardened by being heated, the bias spring 3 is extended, andwhen the heat is released from the shape memory alloy member 1, theshape memory alloy member 1 is softened and extended by a stress of thebias spring 3. Thus, the movable portion 5 for holding the lens 4 ismoved. The control circuit 10 controls the movable portion 5 forpositioning, and controls the overall operations of the image pickupdevice.

FIG. 2 is a block diagram showing the control circuit 10. As shown inFIG. 2, the control circuit 10 includes a drive control circuit 20 (anexample of a drive control section), a microcomputer section 30, astoring section 70, the image sensor 80, and a temperature sensor (anexample of a temperature detecting section). The drive control circuit20 is connected to the shape memory alloy member 1 through theconductive wires 9. The drive control circuit 20 includes a resistancevalue detecting section 21 and a servo controlling section 22. The drivecontrol circuit 20 outputs, to the shape memory alloy member 1, a drivecurrent in accordance with an instruction value for positioning themovable portion 5, changes the temperature of the shape memory alloymember 1, and deforms the shape of the shape memory alloy member 1 tothereby move the movable portion 5.

The resistance value detecting section 21 detects a resistance value ofthe shape memory alloy member 1 at e.g. a predetermined time interval,and outputs the detected resistance value to the microcomputer section30 at e.g. a predetermined time interval. The servo controlling section22 increases/decreases a drive current to be outputted to the shapememory alloy member 1 in such a manner that a resistance value of theshape memory alloy member 1 detected by the resistance value detectingsection 21 becomes equal to a resistance value corresponding to aninstruction value outputted from the microcomputer section 30. In thisembodiment, the servo controlling section 22 stores in advance arelation between instruction values and resistance values, which isobtained by an experiment, and determines a resistance value inaccordance with an instruction value by referring to the relation. Theservo controlling section 22 outputs a drive current value to themicrocomputer section 30 at a predetermined time interval, for instance.

The microcomputer section 30 includes a CPU, an ROM, and an RAM. Themicrocomputer section 30 further includes a computing section 40, atimer 50 (an example of a time measuring section) for measuring a time,and an operation time number counting section 60 (an example of a numbercounting section) for counting the number of times of operation of theshape memory alloy member 1. The computing section 40, the timer 50, andthe operation time number counting section 60 may be realized by causinga CPU to execute a predetermined program, or may be realized by adedicated hardware circuit.

The computing section 40 includes a contact detecting section 41, acorrecting section 42, and a setting section 43. The contact detectingsection 41 detects whether the movable portion 5 is positioned to acontact position in contact with the stopper 7, 8. In this embodiment,the contact detecting section 41 detects whether the movable portion 5is positioned to a first contact position where the movable portion 5 iscontacted with the stopper 7, and detects whether the movable portion 5is positioned to a second contact position where the movable portion 5is contacted with the stopper 8 by detecting a change in the resistancevalue. Specifically, the contact detecting section 41 calculates achange amount of the resistance value, based on resistance values to beoutputted from the resistance value detecting section 21 at apredetermined time interval, determines that the movable portion 5 hasleft the stopper 7, 8, if the calculated change amount becomes largerthan a predetermined value, and determines that the movable portion 5has contacted with the stopper 7, 8, if the calculated change amountbecomes smaller than the predetermined value.

The contact detecting section 41 may detect a contact position bydetecting a change in a current flowing through the shape memory alloymember 1, or a voltage corresponding to the current, in place of using aresistance value. In the modification, the drive control circuit 20 maybe provided with a current detecting section for detecting a currentflowing through the shape memory alloy member 1 and outputting thedetected current to the microcomputer section 30, or a voltage detectingsection for detecting a voltage corresponding to the current andoutputting the detected voltage to the microcomputer section 30, inplace of providing the resistance value detecting section 21.

The storing section 70 stores initial position information fordetermining a relation between a position of the movable portion and aninstruction value in an initial state. In this embodiment, the initialposition information includes a first initial contact instruction value,which is predefined as an instruction value for positioning the movableportion 5 to the first contact position, a second initial contactinstruction value, which is predefined as an instruction value forpositioning the movable portion 5 to the second contact position, and aninitial standby instruction value, which is predefined an instructionvalue for positioning the movable portion 5 to a predetermined standbyposition in the moving range. The first initial contact instructionvalue, the second initial contact instruction value, and the initialstandby instruction value are e.g. values obtained by an experiment in aproduction process.

The correcting section 42 calculates an actual standby instruction valueby correcting the initial standby instruction value, based on a secondactual contact instruction value obtained when the contact detectingsection 41 has detected that the movable portion 5 is positioned to thesecond contact position, and the second initial contact instructionvalue.

In this embodiment, assuming that the second initial contact instructionvalue is Xstop, the initial standby instruction value is Xstby, and thesecond actual contact instruction value is Xstop′, the actual standbyinstruction value Xstby′ is calculated, using e.g. the formula (1).Xstby′=Xstby+(Xstop′−Xstop)  (1)

Alternatively, the correcting section 42 may calculate the actualstandby instruction value Xstby′ by correcting the initial standbyinstruction value Xstby, based on a first actual contact instructionvalue Xstart′ obtained when the contact detecting section 41 hasdetected that the movable portion 5 is positioned to the first contactposition, and the first initial contact instruction value Xstart. In themodification, the actual standby instruction value Xstby′ may becalculated by the following formula (2).Xstby′=Xstby+(Xstart′−Xstart)  (2)

The setting section 43 sets a standby position corresponding to theactual standby instruction value, as the actual standby position of themovable portion 5. Then, in the case where the movable portion 5 ismoved to the standby position, the setting section 43 outputs an actualstandby instruction value to the drive control circuit 20, and the servocontrolling section 22 adjusts the drive current to such a level that aresistance value detected by the resistance value detecting section 21becomes equal to a resistance value corresponding to the actual standbyinstruction value. Thereby, the movable portion 5 is positioned to aspecified standby position.

Further, in the case where the movable portion 5 is positioned to acertain targeted position in the moving range, the setting section 43calculates an instruction value corresponding to the targeted position,and outputs the calculated instruction value to the drive controlcircuit 20 to thereby position the movable portion 5 to the targetedposition. In this embodiment, the setting section 43 stores in advance arelation between the respective positions of the movable portion 5 inthe moving range, and an increment or a decrement of the instructionvalue at the respective positions, based on a standby position as areference. The relation is obtained in advance by an experiment. In thecase where the movable portion 5 is positioned to a certain targetedposition, the setting section 43 calculates an instruction value withrespect to the targeted position by adding or subtracting an incrementor a decrement with respect to the targeted position to or from theactual standby instruction value calculated by the correcting section42; and outputs the calculated instruction value to the drive controlcircuit 20.

The temperature sensor 90 is a temperature sensor such as a thermistor.The image sensor 80 is an image sensor such as a CMOS image sensor or aCCD image sensor. The image sensor 80 captures a subject image under thecontrol of the control circuit 10, and acquires image data of thesubject. The image data is subjected to a predetermined image processingby an unillustrated image processing section, and the processed imagedata is stored into an unillustrated image memory.

FIG. 3 is a graph showing a relation between a position of the movableportion 5, and a resistance value of the shape memory alloy member 1. InFIG. 3, the vertical axis denotes a resistance value, and the horizontalaxis denotes a position of the movable portion 5. Referring to FIG. 3,the position 0 indicates the first contact position, and the positionPmax indicates the second contact position where the movable portion 5is contacted with the stopper 8.

At the position 0, the shape memory alloy member 1 is extended by thebias spring 3, because the drive current to be applied to the shapememory alloy member 1 is small and the temperature of the shape memoryalloy member 1 is low. Accordingly, the movable portion 5 is contactedwith the stopper 7, and is positioned to the first contact position. Atthe point A, the drive current is set to a minimum value, and theresistance value is set to the maximum resistance value Rmax of theshape memory alloy member 1.

As the drive current to be applied to the shape memory alloy member 1 isgradually increased, the resistance value is decreased, and thecontracting force of the shape memory alloy member 1 is increased. Atthe point B where the contracting force exceeds the stress by the biasspring 3, the movable portion 5 leaves the stopper 7, and starts moving.The resistance value at this point of time is set to Rstart.

Thereafter, the movable portion 5 is moved toward the position Pmax bythe contracting force of the shape memory alloy member 1, as the drivecurrent is increased. Then, the movable portion 5 is moved to the pointC when the movable portion 5 is contacted with the stopper 8. At thepoint C, the movable portion 5 is positioned to Pmax, and the resistancevalue of the shape memory alloy member 1 is set to Rstop.

As the drive current is further increased, the resistance value isdecreased. However, since the movement of the movable portion 5 isrestrained by the stopper 8, the movable portion 5 is not changed anymore. At the point D, the drive current becomes a maximum value, and theresistance value becomes the minimum resistance value Rmin of the shapememory alloy member 1.

As described above, the points B and C as inflection points appear inthe graph showing the relation between a position of the movable portion5 and a resistance value. Accordingly, judgment as to whether themovable portion 5 is contacted with the stopper 7, 8 can be made bydetecting a change in the resistance value of the shape memory alloymember 1.

FIG. 4 is a graph showing a relation between a position of the movableportion 5, and a drive current to be applied to the shape memory alloymember 1. At the point A, the drive current is set to the minimum valueImin, the movable portion 5 is contacted with the stopper 7, and theposition of the movable portion 5 is set to 0.

Then, as the drive current is gradually increased, at the point B, themovable portion 5 leaves the stopper 7, and starts moving toward Pmax.At this point of time, the drive current is set to Istart.

Thereafter, as the drive current is increased, the position of themovable portion 5 is increased by contraction of the shape memory alloymember 1. Then, at the point C where the movable portion 5 is contactedwith the stopper 8, the position of the movable portion 5 is set to themaximum value Pmax, and the drive current is set to Istop.

Thereafter, even if the drive current is further increased, displacementof the movable portion 5 is restrained by the stopper 8, and the movableportion 5 is kept unmoved. At the point D, the drive current becomes themaximum value Imax.

As described above, the points B and C as inflection points appear inthe graph showing a relation between a position of the movable portion5, and a drive current. Accordingly, the contact detecting section 41 isallowed to judge whether the movable portion 5 is contacted with thestopper 7, 8 by detecting a change in the current flowing through theshape memory alloy member 1, in place of using a resistance value.

FIG. 5 is a graph showing a relation between an instruction value to beoutputted from the microcomputer section 30, and a resistance value ofthe shape memory alloy member 1. In FIG. 5, the vertical axis denotes aresistance value, and the horizontal axis denotes an instruction value.In the graph shown in FIG. 5, when the instruction value is set to 0,the servo controlling section 22 sets the drive current to a minimumvalue, sets the resistance value to the maximum resistance value Rmax,increases the instruction value, and decreases the resistance value.

At the point A, the instruction value is set to 0, the drive current isset to a minimum value, and the resistance value is set to Rmax. Then,as the instruction value is gradually increased, the servo controllingsection 22 increases the drive current in such a manner that aresistance value corresponding to the instruction value is obtained.Thereby, the resistance value is reduced.

At the point B, the resistance value becomes Rstart, the movable portion5 leaves the stopper 7, and the position of the movable portion 5 startsincreasing. The instruction value at this point of time is set toXstart.

Thereafter, the movable portion 5 is moved in the downward direction bycontraction of the shape memory alloy member 1 resulting from anincrease in the instruction value. Then, at the point C where themovable portion 5 is contacted with the stopper 8, the resistance valueof the shape memory alloy member 1 is set to Rstop, and the instructionvalue is set to Xstop.

As the instruction value is further increased, although the resistancevalue is decreased, the position of the movable portion 5 is keptunchanged, because the movement of the movable portion 5 is restrictedby the stopper 8. In the range D, the drive current is kept to a maximumvalue, and the resistance value is kept to Rmin. In the range D, sincethe servo controlling section 22 saturates the drive current at themaximum value by a restricting circuit, even if the instruction value isincreased, the resistance value is kept to Rmin until the instructionvalue is set to the maximum value Xmax.

FIG. 6 is a graph showing a relation between an instruction value to beoutputted from the microcomputer section 30, and a drive current to beoutputted to the shape memory alloy member 1. At the point A, theinstruction value is set to 0, and the drive current to be applied tothe shape memory alloy member 1 is set to the minimum value Imin.

As the instruction value is gradually increased, the resistance value isdecreased, and the drive current is increased. At the point B, the drivecurrent is set to Istart, and the movable portion 5 leaves the stopper 7and starts moving. The instruction value at this point of time is set toXstart.

Thereafter, as the instruction value is increased, the position of themovable portion 5 is moved in the downward direction by a contractingforce of the shape memory alloy member 1. Then, until the point C wherethe movable portion 5 is contacted with the stopper 8, the position ofthe movable portion 5 is increased, and the drive current is set toIstop at the point C. At this point of time, the instruction value isset to Xstop.

As the instruction value is further increased, the drive current isincreased. However, the position of the movable portion 5 is keptunchanged, because the position of the movable portion 5 is restrictedby the stopper 8. In the range D, the drive current is kept to themaximum value Imax. In the range D, the servo controlling section 22saturates the drive current at the maximum value by the restrictingcircuit. Accordingly, the drive current is kept to the maximum valueuntil the instruction value is set to the maximum value Xmax, even ifthe instruction value is increased.

FIG. 7 is a graph showing a relation between an instruction value to beoutputted from the microcomputer section 30, and a position of themovable portion 5. Referring to FIG. 7, the movable portion 5 is kept incontact with the stopper 7, and positioned to 0 from the point A to thepoint B i.e. from the point of time when the instruction value is set to0 to the point of time when the instruction value is set to Xstart.

Then, as the instruction value is gradually increased, the position ofthe movable portion 5 is gradually increased by servo control, and atthe point C, the position of the movable portion 5 is set to the maximumvalue Pmax. The instruction value at this point of time is set to Xstop.Thereafter, even if the instruction value is increased to Xmax, theposition of the movable portion 5 is kept unchanged, because themovement of the movable portion 5 is restricted by the stopper 8.

FIG. 8 is a diagram showing a relation between a position of the movableportion 5 and an instruction value. The solid-line graph in FIG. 8 is agraph before the relation is changed, and the dotted-line graph in FIG.8 is a graph after the relation is changed. Pstby in FIG. 8 indicates aninitial standby position. Assuming that the instruction value is set toXstby in the solid-line graph, the servo controlling section 22positions the movable portion 5 to the targeted standby position Pstby.

Now, let us assume that the relation between a position of the movableportion 5 and an instruction value is changed from the state shown bythe solid-line graph to the state shown by the dotted-line graph,resulting from e.g. a change in the ambient temperature, or agingdeterioration of members such as the shape memory alloy member 1.

In the above case, if the instruction value is set to Xstby, the movableportion 5 is positioned to Pstby′, which is displaced from the specifiedstandby position Pstby. In this embodiment, assuming that the dottedline graph is shifted in parallel to the horizontal axis with respect tothe solid-line graph, the displacement between Xstop and Xstop′ becomesequal to the displacement between Xstby and Xstby′.

Accordingly, the actual standby instruction value Xstby′, which is aninstruction value for positioning the movable portion 5 to a specifiedstandby position, can be obtained by storing the values Xstop and Xstbyin advance into the storing section 70, allowing the correcting section42 to acquire the second actual contact instruction value Xstop′, whichis an instruction value for actually contacting the movable portion 5with the stopper 8, and substituting the value Xstop′ into the formula(1).

Then, as shown by the dotted line graph in FIG. 8, when the value Xstby′is defined as the instruction value, the movable portion 5 is positionedto the specified standby position Pstby.

Next, an initial sequence for detecting the second initial contactposition and the initial standby position is described. FIG. 9 is aflowchart showing the initial sequence. First, the setting section 43sets an instruction value as an initial value to detect the secondcontact position (Step S1). In this embodiment, it is preferable to usea value sufficiently smaller than a value which is estimated to be thesecond initial contact instruction value, as the initial value.

Then, the servo controlling section 22 moves the movable portion 5 byadjusting the drive current to such a level that a resistance valuedetected by the resistance value detecting section 21 becomes equal to aresistance value corresponding to the instruction value set by thesetting section 43 (Step S2). Then, the contact detecting section 41detects whether the movable portion 5 has contacted with the stopper 8(Step S3). Then, in the case where the contact detecting section 41 hasdetected that the movable portion 5 is contacted with the stopper 8 (YESin Step S3), the setting section 43 writes the instruction value set inthe above case into the storing section 70, as the second initialcontact instruction value Xstop.

If, on the other hand, the judgment result in Step S3 is negative (NO inStep S3), the setting section 43 increases the instruction value by apredetermined value (Step S4), and the routine returns to Step S2. Thus,the operations in Step S2 through Step S4 are repeated to detect thesecond initial contact instruction value Xstop.

Then, the setting section 43 decreases the instruction value by apredetermined value (Step S6). Then, the servo controlling section 22moves the movable portion 5 by adjusting the drive current to such alevel that a resistance value detected by the resistance value detectingsection 21 becomes equal to a resistance value corresponding to theinstruction value set by the setting section 43 (Step S7).

Then, the setting section 43 judges whether the movable portion 5 ispositioned to a targeted standby position (Step S8). In this embodiment,the setting section 43 causes the image sensor 80 to capture an image ofa test chart, and judges whether the movable portion 5 is positioned toa targeted standby position based on the acquired image data. In thisembodiment, a reference focus position at which an image of a subjectaway from the image pickup device by a certain distance is focused, or areference zoom position at which an image of a subject is captured witha certain magnification ratio, is used as a standby position. In thecase where the reference focus position is used as a standby position, atest chart is disposed at a position away from the image pickup deviceby a certain distance to capture an image of the test chart, and theposition of the movable portion 5, at which focused image data isobtained, is defined as the targeted standby position.

In the case where the reference zoom position is used as a standbyposition, a test chart of a predetermined size is disposed at a positionaway from the image pickup device by a predetermined distance to capturean image of the test chart, and the position of the movable portion 5,at which the size of the test chart in the obtained image data becomesequal to a predetermined size, is defined as the targeted standbyposition.

In Step S8, in the case where the setting section 43 judges that themovable portion 5 is positioned to the targeted standby position (YES inStep S8), the instruction value set in the above case is written intothe storing section 70, as the initial standby instruction value Xstby(Step S9).

If, on the other hand, the judgment result in Step S8 is negative (NO inStep S8), the routine returns to Step S6, wherein the setting section 43decreases the instruction value by a predetermined value. As describedabove, the operations in Step S6 through Step S8 are repeated to detectthe initial standby instruction value Xstby.

Thus, the initial sequence is ended. The initial sequence is performedin an adjusting step of a production process of the product, forinstance.

Next, a correction process is described. FIG. 10 is a flowchart showinga correction process. First, the correcting section 42 reads out thesecond initial contact instruction value Xstop from the storing section70 (Step S21). Then, the correcting section 42 reads out the initialstandby instruction value Xstby from the storing section 70 (Step S22).

Then, the setting section 43 sets an instruction value as an initialvalue to detect the second contact position (Step S23). In thisembodiment, it is preferable to use a value sufficiently smaller thanthe second initial contact instruction value, as the initial value.

Then, the servo controlling section 22 moves the movable portion 5 byadjusting the drive current to such a level that a resistance valuedetected by the resistance value detecting section 21 becomes equal to aresistance value corresponding to the instruction value set by thesetting section 43 (Step S24). Then, the contact detecting section 41detects whether the movable portion 5 has contacted with the stopper 8(Step S25). Then, in the case where the contact detecting section 41 hasdetected that the movable portion 5 is contacted with the stopper 8 (YESin Step S25), the correcting section 42 acquires the instruction valueset in the above case, as the second actual contact instruction valueXstop′ (Step S27).

If, on the other hand, the judgment result in Step S25 is negative (NOin Step S25), the setting section 43 increases the instruction value bya predetermined value (Step S26), and the routine returns to Step S24.

Then, the correcting section 42 calculates the actual standbyinstruction value Xstby′ by substituting the second initial contactinstruction value Xstop read out in Step S21, the initial standbyinstruction value Xstby read out in Step S22, and the second actualcontact instruction value Xstop′ acquired in Step S27 into the formula(1) (Step S28).

Then, the setting section 43 sets the actual standby instruction valueXstby′ calculated in Step S28, as an instruction value (Step S29). Then,the servo controlling section 22 moves the movable portion 5 to thestandby position by adjusting the drive current to such a level that aresistance value detected by the resistance value detecting section 21becomes equal to a resistance value corresponding to the instructionvalue set by the setting section 43 (Step S30). Thus, the correctionprocess is ended, the correction sequence is completed, and the imagepickup device is brought to a standby state.

As described above, the shape memory alloy driving device of the firstembodiment is operable to calculate the actual standby instruction valueby correcting the initial standby instruction value, based on adisplacement between the second actual contact instruction valueobtained when the contact detecting section 41 has detected that themovable portion 5 is positioned to the second contact position, and theinitial contact instruction value. Accordingly, the shape memory alloydriving device is advantageous in precisely positioning the movableportion to a specified standby position.

In the above arrangement, the correcting section 42 may perform thecorrection process in response to e.g. turning on of the power source ofthe image pickup device, or in response to detection of a change of adetection temperature by the temperature sensor 90 by a predeterminedvalue. Further alternatively, the correcting section 42 may perform thecorrection process, each time an operation time of the image pickupdevice measured by the timer 50 has exceeded a predetermined time, afterturning on of the power source of the image pickup device.

Further alternatively, the correcting section 42 may perform thecorrection process each time the number of times of operation of theshape memory alloy member 1, which has been counted by the operationtime number counting section 60, is changed by a predetermined value. Inthe modification, the operation time number counting section 60increments the number by one, in the case where the instruction value isset by the setting section 43 to move the movable portion 5 to a certaintargeted position. Further alternatively, the correcting section 42 mayperform the correction process in association with the point of timewhen the power source of the image pickup device is turned on, the pointof time when the detection temperature by the temperature sensor 90 ischanged by a predetermined value, the point of time when a time measuredby the timer 50 has exceeded a predetermined time after turning on ofthe power source of the image pickup device, and/or the point of timewhen the number of times of operation of the shape memory alloy member 1is changed by a predetermined value.

Setting the condition for performing the correction process as describedabove enables to accurately position the movable portion 5 to aspecified targeted position by performing the correction process againif a displacement of the standby position is estimated, and enables toprevent a likelihood that the correction process may be performed, whenunneeded.

In the shape memory alloy driving device, as the number of times ofdriving the shape memory alloy member 1 is increased, agingdeterioration may occur, which may resultantly increase a displacementin the standby position. In view of the above, the correcting section 42may update the second initial contact instruction value and the initialstandby instruction value stored in the storing section 70 with thesecond actual contact instruction value and the actual standbyinstruction value, respectively, in the case where the number of timesof operation counted by the operation time number counting section 60 ischanged by a predetermined value. This arrangement enables to set thesecond initial contact instruction value for seeking the second contactposition to a proper value, even if aging deterioration has occurred,which is advantageous in shortening a time required for a detectionprocess.

In the foregoing description, the contact detecting section 41determines the presence or absence of contact, based on a change in theresistance value. Alternatively, the presence or absence of contact maybe determined by using a contact sensor. FIG. 11 is an externalconstruction diagram of a shape memory alloy driving device providedwith contact sensors 11.

The contact sensors 11 are disposed on a lower surface of a stopper 7,and an upper surface of a stopper 8, respectively. Examples of thecontact sensor 11 are an electrical contact switch and a piezoelectricsensor.

The contact sensors 11 are connected to a control circuit 10 through aconductive wire 12, and output signals indicating contact of the movableportion 5 with the stoppers 7 and 8, respectively. Since the arrangementother than the above in the modification is substantially the same asthe arrangement shown in FIG. 1, description thereof is omitted herein.FIG. 12 is a block diagram of the control circuit 10 shown in FIG. 11.In the case where a contact detecting section 41 receives a signalindicating contact from the upper contact sensor 11, the contactdetecting section 41 judges that the movable portion 5 has contactedwith the stopper 7. In the case where the contact detecting section 41receives a signal indicating non-contact from the upper contact sensor11, the contact detecting section 41 judges that the movable portion 5is away from the stopper 7. Further, the contact detecting section 41judges contact/non-contact of the movable portion 5 with the stopper 8,using the lower contact sensor 11, in the same manner as the uppercontact sensor 11.

In the foregoing description, the storing section 70 stores the firstinitial contact instruction value (Xstart), the second initial contactinstruction value (Xstop), and the initial standby instruction value(Xstby). The invention is not limited to the above. Specifically, thestoring section 70 may store in advance the second initial contactinstruction value (Xstop), and a differential value (=Xstby−Xstop)between the initial standby instruction value (Xstby) and the secondinitial contact instruction value (Xstop). In the modification, thecorrecting section 42 may read out the differential value (=Xstby−Xstop)from the storing section 70, and calculate the actual standbyinstruction value (Xstby′) by implementing the formula (1).

Further alternatively, the storing section 70 may store in advance thefirst initial contact instruction value (Xstart), and a differentialvalue (=Xstby−Xstart) between the initial standby instruction value(Xstby) and the first initial contact instruction value (Xstart). In themodification, the correcting section 42 may read out the differentialvalue (=Xstby−Xstart) from the storing section 70, and calculate theactual standby instruction value (Xstby′) by implementing the formula(2).

(Second Embodiment)

Next, a shape memory alloy driving device as the second embodiment isdescribed. Since the external arrangement and the block diagram in thesecond embodiment are substantially the same as those in the firstembodiment, the second embodiment is described referring to FIGS. 1 and2. Further, description on the elements in the second embodiment, whichare substantially identical or equivalent to those in the firstembodiment, is also omitted herein.

FIG. 13 is a diagram showing a relation between a position of a movableportion 5 and an instruction value. The solid-line graph in FIG. 13 is agraph before the relation between a position of the movable portion 5and an instruction value is changed, and the dotted line graph in FIG.13 is a graph after the relation between a position of the movableportion 5 and an instruction value is changed from an initial state.

The relation between a position of the movable portion 5 and aninstruction value may be shifted along the horizontal axis, and thegradients of the respective graphs may also be changed from each other,resulting from a change in the ambient temperature or agingdeterioration of members such as the shape memory alloy member 1, asshown by the change from the solid-line graph to the dotted-line graph.

Assuming that the instruction value is set to Xstby, the movable portion5 is positioned to Pstby′, which is displaced from a specified standbyposition Pstby. Likewise, Xstart is displaced to Xstart′, and Xstop isdisplaced to Xstop′. Xstart indicates a first initial contactinstruction value.

Based on the above, the actual standby instruction value Xstby′ can beobtained by storing the values Xstart, Xstop, and Xstby in advance intoa storing section 70, allowing a correcting section 42 to acquireXstart′ and Xstop′, which are instructions values for actuallycontacting the movable portion 5 with stoppers 7 and 8 respectively, andsubstituting the values Xstart′ and Xstop′ into the formula (3).(Xstby′−Xstart′):(Xstop′−Xstart′)=(Xstby−Xstart):(Xstop−Xstart)Xstby′=Xstart′+(Xstby−Xstart)×(Xstop′−Xstart′)/(Xstop−Xstart)  (3)

Specifically, the correcting section 42 calculates the actual standbyinstruction value Xstby′ by correcting the initial standby instructionvalue Xstby, based on a differential value between the initial standbyinstruction value Xstby and the first initial contact instruction valueXstart, a differential value between the first actual contactinstruction value Xstart′ and the second actual contact instructionvalue Xstop′, and a differential value between the first initial contactinstruction value Xstart and the second initial contact instructionvalue Xstop.

Next, an initial sequence for detecting a first initial contactposition, a second initial contact position, and an initial standbyposition is described. FIG. 14 is a flowchart showing the initialsequence. First, a setting section 43 sets an instruction value as aninitial value to detect a first contact position (Step S41). In thisembodiment, it is preferable to use a value sufficiently smaller than avalue which is estimated to be the first initial contact instructionvalue, as the initial value.

Then, a servo controlling section 22 moves the movable portion 5 byadjusting a drive current to such a level that a resistance valuedetected by a resistance value detecting section 21 becomes equal to aresistance value corresponding to the instruction value set by thesetting section 43 (Step S42). Then, a contact detecting section 41detects whether the movable portion 5 has left the stopper 7 (Step S43).Then, in the case where the contact detecting section 41 detects thatthe movable portion 5 has left the stopper 7 (YES in Step S43), thesetting section 43 writes the instruction value set in the above caseinto the storing section 70, as the first initial contact instructionvalue Xstart (Step S45).

If, on the other hand, the judgment result in Step S43 is negative (NOin Step S43), the setting section 43 increases the instruction value bya predetermined value (Step S44), and the routine returns to Step S42.Thus, the operations in Step S42 through Step S44 are repeated to detectthe first initial contact instruction value Xstart.

Then, the setting section 43 sets an instruction value as an initialvalue to detect a second contact position (Step S46). Thereafter, theoperations in Step S47 through Step S49 are repeated to detect thesecond contact position. Since the operations in Steps S47 through S50are identical to those in Steps S2 through S5 shown in FIG. 9,description thereof is omitted herein.

Then, the setting section 43 resets the initial value to the firstinitial contact instruction value Xstart, and increases the firstinitial contact instruction value Xstart by a predetermined value (StepS51). Thereafter, the operations in Step S51 through Step S53 arerepeated to move the movable portion 5 to a targeted standby position,detect the initial standby instruction value Xstby, and write theinitial standby instruction value Xstby into the storing section 70.Since the operations in Steps S51 through S54 are identical to those inSteps S6 through S9 shown in FIG. 9, description thereof is omittedherein.

Thus, the initial sequence is ended. The initial sequence is performedin an adjusting step of a production process of the product, forinstance.

Next, a correction process is described. FIG. 15 is a flowchart showinga correction process. First, the correcting section 42 reads out thefirst initial contact instruction value Xstart, the second initialcontact instruction value Xstop, and the initial standby instructionvalue Xstby from the storing section 70 (Steps S61 through S63).

Then, the setting section 43 sets an instruction value as an initialvalue to detect the first contact position (Step S64). In thisembodiment, it is preferable to use a value sufficiently smaller thanthe first initial contact instruction value, as the initial value.

Then, the servo controlling section 22 moves the movable portion 5 byadjusting the drive current to such a level that that a resistance valuedetected by the resistance value detecting section 21 becomes equal to aresistance value corresponding to the instruction value set by thesetting section 43 (Step S65). Then, the contact detecting section 41detects whether the movable portion 5 has left the stopper 7 (Step S66).Then, in the case where the contact detecting section 41 detects thatthe movable portion 5 has left the stopper 7 (YES in Step S66), thecorrecting section 42 acquires the instruction value set by the settingsection 43 in the above case, as the first actual contact instructionvalue Xstart′ (Step S68).

If, on the other hand, the judgment result in Step S66 is negative (NOin Step S66), the setting section 43 increases the instruction value bya predetermined value (Step S67), and the routine returns to Step S65.Since the operations in Step S69 through Step S73 are identical to thosein Step S23 through Step S27 shown in FIG. 10, description thereof isomitted herein.

Then, the correcting section 42 calculates the actual standbyinstruction value Xstby′ by substituting the first initial contactinstruction value Xstart read out in Step S61, the second initialcontact instruction value Xstop read out in Step S62, the initialstandby instruction value Xstby read out in Step S63, the first actualcontact instruction value Xstart′ acquired in Step S66, and the secondactual contact instruction value Xstop′ acquired in Step S73 into theformula (3) (Step S74).

Since the operations in Steps S75 through S76 are identical to those inSteps S29 through S30 shown in FIG. 10, description thereof is omittedherein. Thus, the correction process is ended, the correction sequenceis completed, and an image pickup device is brought to a standby state.

As described above, since the shape memory alloy driving device of thesecond embodiment is operable to calculate the actual standbyinstruction value by correcting the initial standby instruction value,using the formula (3), the shape memory alloy driving device isadvantageous in precisely positioning the movable portion 5 to aspecified standby position.

A condition for performing the correction process in the secondembodiment may be set in the similar manner as the first embodiment.Further alternatively, the contact detecting section 41 may detect thepresence or absence of contact, using contact sensors 11. Furtheralternatively, the first initial contact instruction value and thesecond initial contact instruction value may be updated with the firstactual contact instruction value and the second actual contactinstruction value respectively, and the initial standby instructionvalue may be updated with the actual standby instruction value, eachtime the number of times of operation reaches a predetermined number.

The following is a summary of the embodiments of the invention.

(1) A shape memory alloy driving device includes a movable portion; amoving mechanism portion which includes a shape memory alloy member, andmoves the movable portion; a restraining member which is contactablewith the movable portion to thereby restrain a movement of the movableportion, and defines a moving range of the movable portion; a drivecontrol section which outputs a drive signal in accordance with aninstruction value for positioning the movable portion to the shapememory alloy member, and controls the moving mechanism portion to movethe movable portion by deforming the shape of the shape memory alloymember; a contact detecting section which detects whether the movableportion is positioned to a contact portion in contact with therestraining member; a storing section which stores initial positioninformation for determining a relation between a position of the movableportion and an instruction value in an initial state; a correctingsection which calculates an actual standby instruction value, based onan actual contact instruction value obtained when the contact detectingsection has detected that the movable portion is positioned to thecontact portion, and the initial position information; and a settingsection which sets a standby position corresponding to the actualstandby instruction value, as an actual standby position of the movableportion.

In the above arrangement, the actual standby instruction value iscalculated, based on the actual contact instruction value obtained whenthe contact detecting section has detected that the movable portion ispositioned to the contact portion, and the initial position informationfor determining the relation between a position of the movable portionand an instruction value in the initial state; and the standby positioncorresponding to the actual standby instruction value is set as theactual standby position of the movable portion. Accordingly, even if thestandby position is displaced from a specified standby position,resulting from e.g. a change in the characteristic of the shape memoryalloy member due to a change in the ambient temperature or deteriorationof the shape memory alloy member, the movable portion can be preciselypositioned to the specified standby position.

(2) Preferably, the initial position information may include an initialcontact instruction value which is predefined as an instruction valuefor positioning the movable portion to the contact position, and aninitial standby instruction value which is predefined as an instructionvalue for positioning the movable portion to the standby position, andthe setting section may calculate the actual standby instruction value,based on the actual contact instruction value, the initial contactinstruction value, and the initial standby instruction value.

In the above arrangement, the actual standby instruction value iscalculated, based on the actual contact instruction value obtained whenthe contact detecting section has detected that the movable portion ispositioned to the contact position, the initial contact instructionvalue, and the initial standby instruction value; and the standbyposition corresponding to the actual standby instruction value is set asthe actual standby position of the movable portion. Accordingly, even ifthe standby position is displaced from a specified standby position,resulting from e.g. a change in the characteristic of the shape memoryalloy member due to a change in the ambient temperature or deteriorationof the shape memory alloy member, the movable portion can be preciselypositioned to the specified standby position.

(3) Preferably, the initial position information may include an initialcontact instruction value which is predefined as an instruction valuefor positioning the movable portion to the contact position, and adifferential value between an initial standby instruction value which ispredefined as an instruction value for positioning the movable portionto the standby position, and the initial contact instruction value, andthe setting section may calculate the actual standby instruction value,based on the differential value and the actual contact instructionvalue.

In the above arrangement, the actual standby instruction value iscalculated, based on he differential value between the initial standbyinstruction value and the initial contact instruction value, and theactual contact instruction value obtained when the contact detectingsection has detected that the movable portion is positioned to thecontact position; and the standby position corresponding to the actualstandby instruction value is set as the actual standby position of themovable portion. Accordingly, even if the standby position is displacedfrom a specified standby position, resulting from e.g. a change in thecharacteristic of the shape memory alloy member due to a change in theambient temperature or deterioration of the shape memory alloy member,the movable portion can be precisely positioned to the specified standbyposition.

(4) Preferably, the correcting section may calculate the actual standbyinstruction value, based on a displacement between the actual contactinstruction value and the initial contact instruction value.

In the above arrangement, since the actual standby instruction value iscalculated, based on the displacement between the actual contactinstruction value obtained when the contact detecting section hasdetected that the movable portion is positioned to the contact position,and the initial contact instruction value, the movable portion can beprecisely positioned to a specified standby position.

(5) Preferably, the restraining member may include a first restrainingmember which restrains a movement of the movable portion over one ofupper and lower limits of the moving range, and a second restrainingmember which restrains a movement of the movable portion over the otherof the upper and lower limits of the moving range, the contact detectingsection may detect whether the movable portion is positioned to a firstcontact position where the movable portion is contacted with the firstrestraining member, and detect whether the movable portion is positionedto a second contact position where the movable portion is contacted withthe second restraining member, the initial contact instruction value mayinclude a first initial contact instruction value which is predefined asan instruction value for positioning the movable portion to the firstcontact position, and a second initial contact instruction value whichis predefined as an instruction value for positioning the movableportion to the second contact position, the actual contact instructionvalue may include a first actual contact instruction value obtained whenthe contact detecting section has detected that the movable portion ispositioned to the first contact position, and a second actual contactinstruction value obtained when the contact detecting section hasdetected that the movable portion is positioned to the second contactposition, and the correcting section may calculate the actual standbyinstruction value, based on the first initial contact instruction value,the second initial contact instruction value, the first actual contactinstruction value, and the second actual contact instruction value.

In the above arrangement, since the actual standby instruction value iscalculated, based on the initial standby instruction value, the firstinitial contact instruction value, the second initial contactinstruction value, the first actual contact instruction value, and thesecond actual contact instruction value, the movable portion can beprecisely positioned to a specified standby position.

(6) Preferably, the contact detecting section may detect a change in aresistance value of the shape memory alloy member to thereby detect thecontact position.

In the above arrangement, since the contact position is detected bydetecting a change in the resistance value of the shape memory alloymember, the contact position can be precisely detected. Specifically,there is a large difference between a resistance value change ratio withrespect to a temperature when the shape memory alloy member is notdeformed, and a resistance value change ratio with respect to atemperature when the shape memory alloy member is deformed. Accordingly,the resistance value is greatly changed at a time when the movableportion is about to contact with the restraining member, or is about toleave the restraining member. In view of the above, the presence orabsence of contact of the movable portion with the restraining membercan be precisely detected by detecting a change in the resistance value.Further, the above arrangement enables to detect the presence or absenceof contact, without providing a contact sensor, which is advantageous insaving the space and the cost.

(7) Preferably, the contact detecting section may detect a change in acurrent flowing through the shape memory alloy member or a voltagecorresponding to the current to thereby detect the contact position.

In the above arrangement, since the contact position is detected bydetecting a change in the current flowing through the shape memory alloymember or the voltage corresponding to the current, the contact positioncan be precisely detected. Specifically, when the movement of themovable portion is restricted by the restraining member, the drivecontrol section greatly changes the current or the voltage, if the drivecontrol section is so designed as to perform servo control, while usingthe instruction value as a target value. This arrangement enables toprecisely detect the presence or absence of contact of the movableportion with the restraining member by detecting a change in the currentor the voltage. Further, the above arrangement enables to detect thepresence or absence of contact, without providing a sensor, which isadvantageous in saving the space and the cost.

(8) Preferably, the contact detecting section may be a contact sensorwhich is disposed at such a position as to detect a contact of themovable portion with the restraining member. In this arrangement, sincethe contact of the movable portion with the restraining member isdetected by the contact sensor, the presence or absence of contact canbe securely detected.

(9) Preferably, the movable portion may hold an image pickup lens foruse in an image pickup device, and the standby position may be areference focus position of the image pickup device.

In an image pickup device provided with an auto-focus function, there isa case that the standby position is set to a reference focus positionwhere image data of a subject is approximately focused before start offocus adjustment. The above arrangement enables to precisely positionthe movable portion to a specified reference focus position, even if thereference focus position is displaced from the specified reference focusposition.

(10) Preferably, the movable portion may hold an image pickup lens foruse in an image pickup device, and the standby position may be areference zoom position of the image pickup device. In an image pickupdevice provided with a zoom function, there is a case that the standbyposition is required to be set to a reference zoom position where theentirety of a subject is approximately captured before start of zoomadjustment. The above arrangement enables to precisely position themovable portion to a specified reference zoom position, even if thereference zoom position is displaced from the specified reference zoomposition.

(11) Preferably, the correcting section may calculate the actual standbyinstruction value when a power source of an image pickup device isturned on. In this arrangement, since the actual standby instructionvalue is calculated each time the power source is turned on, the movableportion can be precisely positioned to a specified standby position.

(12) Preferably, the shape memory alloy driving device may furtherinclude a temperature detecting section which detects an ambienttemperature, wherein the correcting section calculates the actualstandby instruction value, when the temperature detected by thetemperature detecting section has changed by a predetermined value. Inthis arrangement, since the actual standby instruction value iscalculated each time the temperature is changed by the predeterminedvalue, the movable portion can be precisely positioned to a specifiedstandby position, even if the standby position is displaced from thespecified standby position resulting from a change in the ambienttemperature.

(13) Preferably, the shape memory alloy driving device may furtherinclude a time measuring section which measures an operation time,wherein the correcting section calculates the actual standby instructionvalue, when the operation time measured by the time measuring sectionhas exceeded a predetermined time. In this arrangement, since the actualstandby instruction value is calculated each time the operation time ischanged by the predetermined value, the movable portion can be preciselypositioned to a specified standby position, even if the standby positionis displaced from the specified standby position, as the operation timeis elapsed.

(14) Preferably, the shape memory alloy driving device may furtherinclude a number counting section which counts the number of times ofoperation, wherein the correcting section calculates the actual standbyinstruction value, when the number of times of operation counted by thenumber counting section has changed by a predetermined value. In thisarrangement, since the actual standby instruction value is calculatedeach time the number of times of operation is changed by thepredetermined value, the movable portion can be precisely positioned toa specified standby position, even if the standby position is displacedfrom the specified standby position due to a long-term use.

(15) Preferably, the shape memory alloy driving device may furtherinclude a number counting section which counts the number of times ofoperation, wherein the correcting section updates the initial contactinstruction value and the initial standby instruction value with theactual contact instruction value and the actual standby instructionvalue respectively, when the number of times of operation counted by thenumber counting section has changed by a predetermined value. In theabove arrangement, since the initial contact instruction value isupdated with a most-recently detected actual contact instruction value,and the initial standby position is updated with a most-recentlydetected actual standby position, the time required for detection can beshortened, which is advantageous in performing a high-speed correctionprocess.

The invention claimed is:
 1. A shape memory alloy driving device,comprising: a movable portion; a moving mechanism portion which includesa shape memory alloy member, and moves the movable portion; arestraining member which is contactable with the movable portion tothereby restrain a movement of the movable portion, and defines a movingrange of the movable portion; a drive control section which outputs adrive signal in accordance with an instruction value for positioning themovable portion to the shape memory alloy member, and controls themoving mechanism portion to move the movable portion by deforming theshape of the shape memory alloy member; a contact detecting sectionwhich detects whether the movable portion is positioned to a contactposition in contact with the restraining member; a storing section whichstores initial position information for determining a relation between aposition of the movable portion and an instruction value in an initialstate; a correcting section which calculates an actual standbyinstruction value, based on an actual contact instruction value obtainedwhen the contact detecting section has detected that the movable portionis positioned to the contact position, and the initial positioninformation; and a setting section which sets a standby positioncorresponding to the actual standby instruction value, as an actualstandby position of the movable portion.
 2. The shape memory alloydriving device according to claim 1, wherein the initial positioninformation includes an initial contact instruction value which ispredefined as an instruction value for positioning the movable portionto the contact position, and an initial standby instruction value whichis predefined as an instruction value for positioning the movableportion to the standby position, and the setting section calculates theactual standby instruction value, based on the actual contactinstruction value, the initial contact instruction value, and theinitial standby instruction value.
 3. The shape memory alloy drivingdevice according to claim 1, wherein the initial position informationincludes an initial contact instruction value which is predefined as aninstruction value for positioning the movable portion to the contactposition, and a differential value between an initial standbyinstruction value which is predefined as an instruction value forpositioning the movable portion to the standby position, and the initialcontact instruction value, and the setting section calculates the actualstandby instruction value, based on the differential value and theactual contact instruction value.
 4. The shape memory alloy drivingdevice according to claim 2, wherein the correcting section calculatesthe actual standby instruction value, based on a displacement betweenthe actual contact instruction value and the initial contact instructionvalue.
 5. The shape memory alloy driving device according to claim 2,wherein the restraining member includes a first restraining member whichrestrains a movement of the movable portion over one of upper and lowerlimits of the moving range, and a second restraining member whichrestrains a movement of the movable portion over the other of the upperand lower limits of the moving range, the contact detecting sectiondetects whether the movable portion is positioned to a first contactposition where the movable portion is contacted with the firstrestraining member, and detects whether the movable portion ispositioned to a second contact position where the movable portion iscontacted with the second restraining member, the initial contactinstruction value includes a first initial contact instruction valuewhich is predefined as an instruction value for positioning the movableportion to the first contact position, and a second initial contactinstruction value which is predefined as an instruction value forpositioning the movable portion to the second contact position, theactual contact instruction value includes a first actual contactinstruction value obtained when the contact detecting section hasdetected that the movable portion is positioned to the first contactposition, and a second actual contact instruction value obtained whenthe contact detecting section has detected that the movable portion ispositioned to the second contact position, and the correcting sectioncalculates the actual standby instruction value, based on the firstinitial contact instruction value, the second initial contactinstruction value, the first actual contact instruction value, and thesecond actual contact instruction value.
 6. The shape memory alloydriving device according to claim 1, wherein the contact detectingsection detects a change in a resistance value of the shape memory alloymember to thereby detect the contact position.
 7. The shape memory alloydriving device according to claim 1, wherein the contact detectingsection detects a change in a current flowing through the shape memoryalloy member or a voltage corresponding to the current to thereby detectthe contact position.
 8. The shape memory alloy driving device accordingto claim 1, wherein the contact detecting section is a contact sensorwhich is disposed at such a position as to detect a contact of themovable portion with the restraining member.
 9. The shape memory alloydriving device according to claim 1, wherein the movable portion holdsan image pickup lens for use in an image pickup device, and the standbyposition is a reference focus position of the image pickup device. 10.The shape memory alloy driving device according to claim 1, wherein themovable portion holds an image pickup lens for use in an image pickupdevice, and the standby position is a reference zoom position of theimage pickup device.
 11. The shape memory alloy driving device accordingto claim 1, wherein the correcting section calculates the actual standbyinstruction value when a power source of an image pickup device isturned on.
 12. The shape memory alloy driving device according to claim1, further comprising: a temperature detecting section which detects anambient temperature, wherein the correcting section calculates theactual standby instruction value, when the temperature detected by thetemperature detecting section has changed by a predetermined value. 13.The shape memory alloy driving device according to claim 1, furthercomprising: a time measuring section which measures an operation time,wherein the correcting section calculates the actual standby instructionvalue, when the operation time measured by the time measuring sectionhas exceeded a predetermined time.
 14. The shape memory alloy drivingdevice according to, claim 1, further comprising: a number countingsection which counts the number of times of operation, wherein thecorrecting section calculates the actual standby instruction value, whenthe number of times of operation counted by the number counting sectionhas changed by a predetermined value.
 15. The shape memory alloy drivingdevice according to claim 2, further comprising: a number countingsection which counts the number of times of operation, wherein thecorrecting section updates the initial contact instruction value and theinitial standby instruction value with the actual contact instructionvalue and the actual standby instruction value respectively, when thenumber of times of operation counted by the number counting section haschanged by a predetermined value.
 16. A shape memory alloy drivingdevice, comprising; a movable portion; a moving mechanism portion whichincludes a shape memory alloy member, and moves the movable portion; arestraining member which is contactable with the movable portion tothereby restrain a movement of the movable portion, and defines a movingrange of the movable portion; a drive control section which outputs adrive current in accordance with an instruction value for positioningthe movable portion to the shape memory alloy member, and controls themoving mechanism portion to move the movable portion by deforming theshape of the shape memory alloy member; a contact detecting sectionwhich detects whether the movable portion is positioned to a contactposition in contact with the restraining member by detecting a change ofthe drive current; a storing section which stores initial positioninformation for determining a relation between a position of the movableportion and an instruction value in an initial state; a correctingsection which calculates an actual standby instruction value, based onan actual contact instruction value obtained when the contact detectingsection has detected that the movable portion is positioned to thecontact position, and the initial position information; and a settingsection which sets a standby position corresponding to the actualstandby instruction value, as an actual standby position of the movableportion, wherein the drive control section adjusts the drive current tosuch a level that a resistance value of the shape memory alloy memberbecomes equal to a resistance value corresponding to the instructionvalue, and wherein the contact detecting section detects the contactposition by detecting an inflection point of the drive current whichappears as the instruction value is gradually increased.
 17. The shapememory alloy driving device according to claim 16, wherein the initialposition information includes an initial contact instruction value whichis predefined as an instruction value for positioning the movableportion to the contact position, and an initial standby instructionvalue which is predefined as an instruction value for positioning themovable portion to the standby position, and the setting sectioncalculates the actual standby instruction value, based on the actualcontact instruction value, the initial contact instruction value, andthe initial standby instruction value.
 18. The shape memory alloydriving device according to claim 17, wherein the initial positioninformation includes an initial contact instruction value which ispredefined as an instruction value for positioning the movable portionto the contact position, and a differential value between an initialstandby instruction value which is predefined as an instruction valuefor positioning the movable portion to the standby position, and theinitial contact instruction value, and the setting section calculatesthe actual standby instruction value, based on the differential valueand the actual contact instruction value.
 19. The shape memory alloydriving device according to claim 18, wherein the correcting sectioncalculates the actual standby instruction value, based on a displacementbetween the actual contact instruction value and the initial contactinstruction value.
 20. The shape memory alloy driving device accordingto claim 18, wherein the restraining member includes a first restrainingmember which restrains a movement of the movable portion over one ofupper and lower limits of the moving range, and a second restrainingmember which restrains a movement of the movable portion over the otherof the upper and lower limits of the moving range, the contact detectingsection detects whether the movable portion is positioned to a firstcontact position where the movable portion is contacted with the firstrestraining member, and detects whether the movable portion ispositioned to a second contact position where the movable portion iscontacted with the second restraining member, the initial contactinstruction value includes a first initial contact instruction valuewhich is predefined as an instruction value for positioning the movableportion to the first contact position, and a second initial contactinstruction value which is predefined as an instruction value forpositioning the movable portion to the second contact position, theactual contact instruction value includes a first actual contactinstruction value obtained when the contact detecting section hasdetected that the movable portion is positioned to the first contactposition, and a second actual contact instruction value obtained whenthe contact detecting section has detected that the movable portion ispositioned to the second contact position, and the correcting sectioncalculates the actual standby instruction value, based on the firstinitial contact instruction value, the second initial contactinstruction value, the first actual contact instruction value, and thesecond actual contact instruction value.